Germanium-silicon quantum well material and preparation method and application thereof

Abstract

The invention discloses a germanium-silicon quantum well material and a preparation method and application thereof. The germanium-silicon quantum well material sequentially comprises a germanium-silicon substrate layer, a germanium-silicon buffer layer, a first potential barrier layer, a potential well layer and a second potential barrier layer from bottom to top, wherein the component contents of the germanium element and the silicon element in at least one of the first barrier layer, the potential well layer and the second barrier layer are respectively in a gradual change state; wherein the gradual change state comprises gradually increasing, decreasing and / or fluctuating change from bottom to top. The germanium-silicon quantum well material can be applied to precise quantum devices, and can effectively solve the problem of surface charge accumulation in the grid control process of germanium-silicon quantum devices, so that the performance of various germanium-silicon grid control quantum devices is optimized.

Description

Technical Field

[0001] The present application relates to the technical field of quantum well materials, and in particular to a germanium silicon quantum well material and a preparation method and application thereof. Background Art

[0002] Semiconductor germanium silicon quantum wells are widely used in quantum devices such as two-dimensional electron (hole) gas, high mobility field effect transistors, gate-controlled quantum dots, and quantum bits due to their excellent material properties. The quantum well material of germanium silicon / silicon / germanium silicon configuration has a mature micro-nano processing technology, and the quantum devices prepared by it have good scalability and integrability. 72 germanium 28 In silicon quantum well materials, there is only a weak hyperfine interaction between the carrier spin and the nuclear spin of the material. This material is an important candidate material for building semiconductor quantum computing chips. On the other hand, quantum wells in the configuration of germanium silicon / germanium / germanium silicon have a strong spin-orbit coupling effect, which can construct hole-type quantum bits that are fully electrically controlled and realize ultrafast manipulation of quantum bits. It can also be combined with superconducting materials to realize novel topological quantum devices. However, the performance of the above quantum devices is limited by the surface charge accumulation effect. During the gate control process, carriers will tunnel to the surface of the material and form charge accumulation, thereby destroying the stable energy state of these quantum devices. The academic community has long paid great attention to technical methods to suppress or completely eliminate surface charge accumulation, and the exploration of new technologies mainly includes two aspects: device preparation process optimization and material optimization.

[0003] In the performance optimization schemes of quantum devices related to germanium silicon quantum wells in the past, attention was often paid to the preparation process of the gate dielectric, the material growth process, and the changes in the quantum well structure. By optimizing the gate dielectric preparation and material growth processes, the defect state density on the material surface can be effectively reduced, thereby reducing charge accumulation. The optimization scheme for the quantum well material structure only focuses on the fixed components and thickness of each layer of material to change the distance from the surface charge to the functional area of ​​the device to reduce the impact of charge accumulation on device performance. However, the above method cannot eliminate the charge accumulation problem. With the increase of the gate control electric field and the accumulation of gate control time, the gradually enriched surface charge will still destroy the stability of the device.

[0004] In order to further develop precision quantum devices such as high-fidelity quantum bits, other technical methods need to be developed to suppress or eliminate surface charges. Summary of the invention

[0005] In order to solve the above-mentioned deficiencies in the art, the present application aims to provide a germanium silicon quantum well material and a preparation method and application thereof.

[0006] According to one aspect of the present application, a germanium-silicon quantum well material is provided, which includes, from bottom to top: a germanium-silicon substrate layer, a germanium-silicon buffer layer, a first barrier layer, a potential well layer, and a second barrier layer;

[0007] The composition contents of germanium and silicon in at least one of the first barrier layer, the potential well layer, and the second barrier layer are in a gradient state;

[0008] The gradual change state includes gradually increasing, decreasing, and / or fluctuating from bottom to top.

[0009] According to some embodiments of the present application, the crystal planes of the germanium silicon quantum well material include (001), (110) and (111) crystal planes.

[0010] According to some embodiments of the present application, the gradual change state includes:

[0011] The gradient range of the germanium content in the first barrier layer, the potential well layer and the second barrier layer is 0%-100%, and the corresponding gradient range of the silicon content is 100%-0%;

[0012] According to some embodiments of the present application, the gradual change state includes: continuous gradual change, step-by-step gradual change and periodic gradual change.

[0013] According to some embodiments of the present application, the thickness of the first barrier layer and the second barrier layer is 1-150 nm;

[0014] The thickness of the potential well layer is 1-50 nm.

[0015] According to some embodiments of the present application, the first barrier layer and the second barrier layer are doped with one or more of boron, aluminum, gallium, indium, phosphorus, arsenic and antimony elements;

[0016] According to some embodiments of the present application, the doping concentration is 0-1×10 18 cm -3 .

[0017] According to some embodiments of the present application, a spacer layer and a modulation doping layer are further provided between the first barrier layer and the potential well layer, and / or between the potential well layer and the second barrier layer;

[0018] The spacer layer is located between the modulation doping layer and the potential well layer.

[0019] According to some embodiments of the present application, the thickness of the modulation doping layer is 0-50 nm;

[0020] Optionally, the modulation doping layer is doped with one or more of boron, aluminum, gallium, indium, phosphorus, arsenic and antimony elements;

[0021] Further optionally, the doping concentration of the modulation doping layer is 1×10 16-5×10 20 cm -3 .

[0022] According to some embodiments of the present application, the thickness of the spacer layer is 0-60 nm;

[0023] Optionally, the germanium element and the silicon element in the spacer layer are in a gradient state, and the gradient range of the gradient state is 0%-100%.

[0024] According to another aspect of the present application, a method for preparing the above-mentioned germanium silicon quantum well material is also provided, comprising:

[0025] Pre-treating the silicon germanium substrate layer;

[0026] epitaxially growing a germanium silicon buffer layer on the first surface of the pretreated germanium silicon substrate layer;

[0027] Epitaxially growing a first barrier layer on a surface of the germanium silicon buffer layer away from the germanium silicon substrate layer;

[0028] Epitaxially growing a potential well layer on a surface of the first potential barrier layer away from the germanium silicon buffer layer;

[0029] epitaxially growing a second barrier layer on a surface of the potential well layer away from the first barrier layer;

[0030] Wherein, the ratio of the growth rates of germanium and silicon is dynamically adjusted during the process of growing at least one of the first barrier layer, the potential well layer and the second barrier layer.

[0031] According to some embodiments of the present application, the method further includes: epitaxially growing a spacer layer and a modulation doping layer;

[0032] Wherein, the spacer layer is located between the modulation doping layer and the potential well layer.

[0033] According to some embodiments of the present application, epitaxial growth includes: molecular beam epitaxy, chemical vapor deposition and physical vapor deposition.

[0034] According to another aspect of the present application, there is provided an application of the above-mentioned germanium silicon quantum well material, and / or the germanium silicon quantum well material prepared by the above-mentioned preparation method in a precision quantum device;

[0035] Among them, precision quantum devices include: quantum bits, two-dimensional electron (hole) gas, field effect transistors, and gate-controlled quantum dots.

[0036] Compared with the prior art, this application has at least the following beneficial effects:

[0037] The present application provides a germanium silicon quantum well material and a preparation method thereof. The material is based on band engineering design and has a germanium silicon component content and doping concentration that gradually changes with the depth of the sample. The germanium silicon quantum well material of the present application can be applied to precision quantum devices, and can effectively solve the surface charge accumulation problem in the gate control process of germanium silicon quantum devices, thereby optimizing the performance of various types of germanium silicon gate-controlled quantum devices, for example: improving the decoherence time of germanium silicon quantum bits, improving the transport performance of two-dimensional carrier gas, and improving the energy stability of gate-controlled quantum dots, field-effect transistors and other devices, which is conducive to the precise construction of quantum systems and promotes the development of quantum technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the structure of the germanium silicon quantum well material of Example 1 of this application

[0039] Figure 2 This is an X-ray diffraction scanning pattern (XRD-mapping) of the germanium silicon quantum well material of Example 1 of the present application.

[0040] Figure 3 This is an atomic force microscope image of the surface of the germanium silicon quantum well material of Example 1 of the present application.

[0041] Figure 4 This is the secondary ion mass spectrometry (SIMS) spectrum line of the germanium silicon quantum well material of Example 1 of the present application.

[0042] Figure 5 This is a schematic diagram of energy band simulation when voltage is applied to the germanium silicon quantum well material of Example 1 of the present application.

[0043] Figure 6 This is the X-ray diffraction surface scan pattern of the germanium silicon quantum well material of comparative example 1 of the present application.

[0044] Figure 7 This is a schematic diagram of energy band simulation when voltage is applied to the germanium silicon quantum well material of comparative example 1 of the present application.

[0045] Figure 8 This is an image of the planar quantum Hall device of Example 2 of the present application taken under an optical microscope.

[0046] Fig. 9 This is a curve showing the change in turn-on voltage (Vt.o.) versus gate control voltage (Vmin) of the planar quantum Hall device of Example 2 of the present application.

[0047] Fig.10 This is a curve showing how the turn-on voltage (Vt.o.) of the planar quantum Hall device of comparative example 2 of the present application changes with the gate control voltage (Vmin).

[0048] Fig.11This is a schematic diagram of energy band simulation when voltage is applied to the germanium silicon quantum well material of Example 3 of the present application. DETAILED DESCRIPTION

[0049] The technical solution of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0050] It is particularly important to point out that similar substitutions and modifications made to the present application are obvious to those skilled in the art, and they are all deemed to be included in the present application. Relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present application to implement and apply the technology of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments.

[0051] If no specific conditions are specified in this application, the preparation shall be carried out under conventional conditions or the conditions recommended by the manufacturer. The raw materials or excipients used, as well as the reagents or instruments used, for which the manufacturers are not specified, are all conventional products that can be obtained commercially.

[0052] The application is described in detail below.

[0053] In the context of this application, a "potential well layer" refers to a material layer where charge carriers gather under the effect of quantum confinement.

[0054] In the context of this application, a "barrier layer" refers to a material layer that provides quantum confinement for charge carriers.

[0055] In the context of the present application, “spacer layer” refers to a material layer used to separate a potential well layer and a doping layer in the case of modulation doping.

[0056] In the context of this application, "composition gradient" means that the content ratio of germanium and silicon elements gradually changes with different depths from the material surface, and the change mode includes continuous gradient, step gradient and periodic gradient with depth.

[0057] In the context of this application, "doping" includes doping of boron, aluminum, gallium, indium, phosphorus, arsenic, and antimony elements into germanium silicon materials.

[0058] In the context of this application, a "Ge-Si virtual substrate" refers to a substrate having a specific Ge-Si content ratio obtained by epitaxial growth on a silicon or germanium wafer, wherein the surface structure of the substrate has a constant Ge-Si content and is stress relaxed.

[0059] In the context of this application, "epitaxial growth" includes molecular beam epitaxy, chemical vapor deposition, and physical vapor deposition.

[0060] High-quality germanium-silicon quantum well materials are the basis for building novel germanium-silicon quantum devices. The main technical approaches for preparing germanium-silicon quantum well materials are as follows: using molecular beam epitaxy or chemical vapor deposition technology, the first barrier layer, the potential well layer, and the second barrier layer with fixed germanium-silicon component content are sequentially grown on the germanium-silicon virtual substrate to form a germanium-silicon quantum well structure. The material performance can be further optimized by regulating the growth temperature, growth rate, or thickness of each layer in the quantum well structure.

[0061] Currently, the performance of quantum devices is limited by the surface charge pile-up effect. During the gate control process, carriers tunnel to the surface of the material and form charge pile-up, which destroys the stable energy state of these quantum devices.

[0062] In order to solve the technical problems currently existing in this field, the present application provides a germanium silicon quantum well material. Different from the fixed component content design in the previous materials, the material is based on band engineering design and has a germanium silicon component content and doping concentration that gradually changes with depth. The present application also provides a method for preparing the above-mentioned germanium silicon quantum well material, including: epitaxially growing a germanium silicon buffer layer on a germanium silicon virtual substrate; epitaxially growing a barrier layer and a potential well layer on the germanium silicon buffer layer, modulating the doping layer and the spacing layer to obtain a quantum well structure.

[0063] The germanium silicon quantum well material of the present application can solve the problem of surface charge accumulation during the gate control process of germanium silicon quantum devices, thereby optimizing the performance of various types of germanium silicon gate-controlled quantum devices.

[0064] The germanium silicon quantum well material of the present application comprises, from bottom to top, a germanium silicon substrate layer, a germanium silicon buffer layer, a first barrier layer, a potential well layer, and a second barrier layer;

[0065] The composition contents of germanium and silicon in at least one of the first barrier layer, the potential well layer, and the second barrier layer are in a gradient state;

[0066] The gradual change state is gradually increasing or decreasing from bottom to top or showing a fluctuating change.

[0067] Optionally, the first barrier layer and the second barrier layer are doped with one or more of boron, aluminum, gallium, indium, phosphorus, arsenic and antimony.

[0068] Optionally, a spacer layer and a modulation doping layer are provided between the first barrier layer and the potential well layer, and / or between the potential well layer and the second barrier layer;

[0069] The spacer layer is located between the modulation doping layer and the potential well layer.

[0070] The crystal planes of the material include (001), (111), and (110).

[0071] The thickness of the barrier layer is 1-150nm. The composition gradient range of the germanium content of the barrier layer is 0%-100%, and the corresponding composition gradient range of the silicon content is 100%-0%. The doping concentration of the barrier layer varies from 0-1×10 18 cm -3 .

[0072] The thickness of the potential well layer is 1-50 nm. The composition gradient range of the germanium element content of the potential well layer is 0%-100%, and the corresponding composition gradient range of the silicon element content is 100%-0%.

[0073] The thickness of the spacer layer is 0-60nm. The composition gradient range of the germanium element content of the spacer layer is 0%-100%, and the corresponding composition gradient range of the silicon element content is 100%-0%.

[0074] The thickness of the modulation doping layer is 0-50nm. The doping concentration of the modulation doping layer varies in the range of 1×10 16 -5×10 20 cm -3 .

[0075] The method for preparing the germanium silicon quantum well material of the present application comprises: epitaxially growing a germanium silicon buffer layer on a germanium silicon virtual substrate; and epitaxially growing a barrier layer, a potential well layer, a modulation doping layer and a spacer layer on the germanium silicon buffer layer to obtain a quantum well structure.

[0076] Wherein, epitaxially growing a germanium silicon buffer layer on a germanium silicon virtual substrate comprises:

[0077] The SiGe virtual substrate is immersed in a diluted hydrogen fluoride solution, taken out and placed in a growth chamber for high-temperature pretreatment. Subsequently, a SiGe buffer layer having the same SiGe component content as the substrate surface is epitaxially grown on the SiGe virtual substrate. The growth temperature is 320-550°C and the growth rate is 0.05-1nm / s.

[0078] Wherein, a barrier layer, a potential well layer, a modulation doping layer and a spacer layer are epitaxially grown on the germanium silicon buffer layer to obtain a quantum well structure, including:

[0079] First, the first barrier layer of the quantum well is epitaxially grown on the germanium-silicon buffer layer at 320-550°C and a growth rate of 0.05-1nm / s. As the growth proceeds, the ratio of the germanium and silicon growth rates is dynamically adjusted to achieve a gradual change in the germanium-silicon composition at different depths of the barrier layer.

[0080] The potential well layer is epitaxially grown on the potential barrier layer at a growth temperature of 320-500°C and a growth rate of 0.05-1nm / s. The ratio of the growth rates of germanium and silicon is dynamically adjusted as the growth proceeds to achieve a gradual change in the germanium-silicon composition at different depths of the potential well layer.

[0081] The second barrier layer is epitaxially grown on the potential well layer at a growth temperature of 310-550° C. and a growth rate of 0.05-1 nm / s. The ratio of the growth rates of germanium and silicon is dynamically adjusted as the growth proceeds to achieve a gradual change in the germanium-silicon composition at different depths of the second barrier layer.

[0082] In some embodiments of the present application, the ratio of the growth rates of germanium and silicon is dynamically adjusted during the growth of at least one of the first barrier layer, the well layer, and the second barrier layer.

[0083] Optionally, epitaxial growth of a modulation doping layer and a spacer layer is selectively inserted between the epitaxial growth steps of the first barrier layer, the potential well layer and the second barrier layer.

[0084] Optionally, the growth temperature of the modulation doping layer is 320-550° C., and the growth rate is 0.05-1 nm / s. The doping is achieved by synchronously depositing impurity elements during the epitaxial growth process.

[0085] Optionally, the growth temperature of the spacer layer is 320-550° C., and the growth rate ranges from 0.05-1 nm / s. As the growth proceeds, the ratio of the growth rates of germanium and silicon is dynamically adjusted to achieve a gradual change of the germanium-silicon composition at different depths of the spacer layer.

[0086] The above-mentioned germanium silicon quantum well material of the present application or the germanium silicon quantum well material prepared by the above-mentioned method is used in precision quantum devices such as quantum bits, two-dimensional electron (hole) gas, high mobility field effect transistors, gate-controlled quantum dots, etc.

[0087] The technical solution of the present application is further described below in conjunction with specific embodiments.

[0088] Example 1

[0089] Prepare the germanium silicon quantum well material of the present application.

[0090] (1) Using molecular beam epitaxy technology, a germanium-silicon buffer layer with a fixed germanium content of 79% is epitaxially grown on a germanium-silicon (001) virtual substrate:

[0091] A Germanium-Silicon (001) virtual substrate was selected, and the surface layer of the substrate had a fixed Germanium-Silicon content, wherein the Germanium content was 79%, and stress was relaxed. The substrate was soaked in a diluted hydrogen fluoride solution for 1 minute; it was taken out and placed in the growth chamber of a molecular beam epitaxy device, and high-temperature pretreatment was performed at 650°C. A 300nm thick Germanium-Silicon buffer layer was epitaxially grown at 450°C, wherein the growth rate of the Germanium element was 0.079nm / s, the growth rate of the Silicon element was 0.021nm / s, and the total material growth rate was 0.1nm / s.

[0092] (2) epitaxially growing a germanium-silicon quantum well material with a gradient composition on the germanium-silicon buffer layer using molecular beam epitaxy technology:

[0093] A first barrier layer with a thickness of 100 nm was epitaxially grown at 450°C on the germanium silicon buffer layer. The growth rate of germanium in the first barrier layer was 0.079 nm / s, the growth rate of silicon was 0.021 nm / s, and the total material growth rate was 0.1 nm / s. A 15 nm thick potential well layer was epitaxially grown at 450°C on the first barrier layer. The germanium content of the potential well layer was 100%, the germanium growth rate was 0.079 nm / s, and the silicon growth rate was 0 nm / s. Subsequently, a 35 nm thick second barrier layer was epitaxially grown at 390°C on the potential well layer. During the growth of the second barrier layer, the germanium growth rate gradually decreased from 0.079 nm / s to 0.01 nm / s, the silicon growth rate gradually increased from 0.021 nm to 0.04 nm / s, and the total growth rate gradually decreased from 0.1 nm / s to 0.05 nm / s. The germanium content of the obtained second barrier layer changes with thickness, from an initial 79% to 20%, and the corresponding silicon content changes from an initial 21% to 80%.

[0094] Example 2

[0095] Application of the germanium silicon quantum well material of Example 1 of the present application.

[0096] The germanium silicon quantum well material of Example 1 is prepared into a planar quantum Hall device using micro-nano processing technology:

[0097] First, the structure of the planar Hall device is etched on the germanium silicon quantum well material using ultraviolet exposure technology and reactive ion etching technology. Then, metal palladium electrodes are prepared on the source and drain regions and voltage measurement regions of the planar Hall device structure by combining ultraviolet exposure technology, electron beam evaporation technology and thermal annealing technology. Then, an aluminum oxide gate dielectric layer is prepared by atomic layer deposition technology. Finally, the titanium gold top gate of the planar Hall device is prepared by combining ultraviolet exposure technology and electron beam evaporation technology.

[0098] Figure 8 This is an image of the planar quantum Hall device prepared in Example 2 of the present application taken under an optical microscope. Figure 8The area marked with a dotted line shows the area where gate-controlled two-dimensional hole gas is formed.

[0099] Fig. 9 This is a curve showing the change of the turn-on voltage of the planar quantum Hall device prepared in Example 2 of the present application as a function of the gate control voltage. Fig. 9 The energy stability of the planar quantum Hall device prepared in Example 2 is shown. In the gate control voltage range of -0.2V to -0.7V, the turn-on voltage of the planar quantum Hall device is stable, indicating that no charge surface accumulation occurs in the gate control range of -0.2V to -0.7V.

[0100] Example 3

[0101] This embodiment is used to illustrate the germanium silicon quantum well material and the preparation method thereof of the present application.

[0102] (1) Using molecular beam epitaxy technology, a germanium-silicon buffer layer with a fixed germanium content of 20% is epitaxially grown on a germanium-silicon (001) virtual substrate:

[0103] A Germanium-Silicon (001) virtual substrate was selected, and the surface layer of the substrate had a fixed Germanium-Silicon content, wherein the Germanium content was 20%, and stress was relaxed. The substrate was soaked in a diluted hydrogen fluoride solution for 1 minute; it was taken out and placed in the growth chamber of a molecular beam epitaxy device, and high-temperature pretreatment was performed at 650°C. Then, a 300nm thick Germanium-Silicon buffer layer was epitaxially grown at 450°C, wherein the growth rate of the Germanium element was 0.020nm / s, the growth rate of the Silicon element was 0.080nm / s, and the total material growth rate was 0.1nm / s.

[0104] (2) epitaxially growing a germanium-silicon quantum well material with a gradient composition on the germanium-silicon buffer layer using molecular beam epitaxy technology:

[0105] First, a 20 nm thick modulation doping layer is epitaxially grown on the germanium silicon buffer layer at 450° C. The impurity element in the modulation doping layer is phosphorus, and the doping concentration is 1×10 17 cm -3. Subsequently, a 20nm thick spacer layer is epitaxially grown on the modulated doping layer at 450°C. During the growth of the spacer layer, the growth rate of germanium gradually increases from 0.020nm / s to 0.050nm / s, and the growth rate of silicon gradually decreases from 0.080nm / s to 0.050nm / s. The total growth rate remains unchanged at 0.10nm / s. The germanium content of the resulting spacer layer varies with thickness, from the initial 20% to 50%, and the silicon content changes from the initial 80% to 50%. Then, a 15nm thick potential well layer is epitaxially grown on the spacer layer at 450°C. The potential well layer has a germanium content of 0%, a silicon content of 100%, and a silicon growth rate of 0.050nm / s. Subsequently, a 35nm thick second barrier layer was epitaxially grown at 390°C on the potential well layer. During the growth of the barrier layer, the growth rate of germanium gradually increased from 0.050nm / s to 0.1nm / s, and the growth rate of silicon gradually decreased from 0.050nm to 0nm / s, with the total growth rate maintained at 0.10nm / s. The germanium content of the obtained second barrier layer changes with thickness, from the initial 50% to 100%, and the corresponding silicon content changes from the initial 50% to 0%.

[0106] Comparative Example 1

[0107] This comparative example prepares a conventional germanium silicon quantum well material without component gradient, which is used to compare and illustrate that the germanium silicon quantum well material of the present application solves the problem of surface charge accumulation under gate control.

[0108] (1) Using molecular beam epitaxy technology, a germanium-silicon buffer layer with a fixed germanium content of 79% is epitaxially grown on a germanium-silicon (001) virtual substrate:

[0109] A Germanium-Silicon (001) virtual substrate was selected, and the surface layer of the substrate had a fixed Germanium-Silicon content, of which the Germanium content was 79%, and the stress was relaxed. The substrate was soaked in a diluted hydrogen fluoride solution for 1 minute. It was taken out and placed in the growth chamber of the molecular beam epitaxy equipment, and high-temperature pretreatment was performed at 650°C. Then, a 300nm thick Germanium-Silicon buffer layer was epitaxially grown at 450°C, in which the growth rate of the Germanium element was 0.079nm / s, the growth rate of the Silicon element was 0.021nm / s, and the total material growth rate was 0.1nm / s.

[0110] (2) epitaxially growing a germanium-silicon quantum well material with a fixed component content on the germanium-silicon buffer layer using molecular beam epitaxy technology:

[0111] First, a first barrier layer with a thickness of 100 nm is epitaxially grown at 450°C on the germanium silicon buffer layer. The growth rate of the germanium element in the barrier layer is 0.079 nm / s, the growth rate of the silicon element is 0.021 nm / s, and the total material growth rate is 0.1 nm / s. Then, a potential well layer with a thickness of 15 nm is epitaxially grown at 450°C on the first barrier layer. The germanium content of the potential well layer is 100%, the growth rate of germanium is 0.079 nm / s, and the growth rate of silicon is 0 nm / s. Subsequently, a second barrier layer with a thickness of 35 nm is epitaxially grown at 390°C on the potential well layer. The growth rate of germanium in the barrier layer is 0.079 nm / s, the growth rate of silicon is 0.021 nm / s, and the total material growth rate is 0.1 nm / s. The germanium content in the second barrier layer is fixed at 79%.

[0112] Comparative Example 2

[0113] Comparative Example 1 shows the application of conventional germanium silicon quantum well material without component gradient.

[0114] It is used for comparison to illustrate that the hole gas quantum device in Example 2 solves the problem of charge surface accumulation.

[0115] The germanium silicon quantum well material of comparative example 1 is prepared into a planar quantum Hall device using micro-nano processing technology:

[0116] First, the structure of the planar Hall device is etched on the germanium silicon quantum well material using ultraviolet exposure technology and reactive ion etching technology. Then, metal palladium electrodes are prepared on the source and drain regions and voltage measurement regions of the planar Hall device structure by combining ultraviolet exposure technology, electron beam evaporation technology and thermal annealing technology. Then, an aluminum oxide gate dielectric layer is prepared by atomic layer deposition technology. Finally, the titanium gold top gate of the planar Hall device is prepared by combining ultraviolet exposure technology and electron beam evaporation technology.

[0117] Fig.10 This is a curve showing the change of the turn-on voltage of the planar quantum Hall device prepared in comparative example 2 of the present application as a function of the gate control voltage. Fig.10 It shows that the energy stability of the planar quantum Hall device prepared in Comparative Example 2 is weaker than that of the planar quantum Hall device in Example 2. In the range of gate control voltage from -0.25V to -0.4V, the turn-on voltage of the planar quantum Hall device changes by -0.08V, indicating that charge surface accumulation occurs when the gate control range exceeds -0.25V.

[0118] Experimental example

[0119] 1. Comparative testing of the germanium silicon quantum well materials of Example 1 and Comparative Example 1 of the present application.

[0120] Figure 1 It is a schematic diagram of the structure of the germanium silicon quantum well material prepared in Example 1 of the present application.

[0121] Figure 2 This is the X-ray diffraction scanning spectrum (XRD-mapping) of the germanium silicon quantum well material prepared in Example 1 of the present application. Figure 2 The intensity peak marked by the middle triangle shows that the step (1) of Example 1 prepared a germanium silicon buffer layer with a germanium content of 79%. Figure 2 The intensity peak marked by the middle triangle also shows that the first barrier layer with a germanium content of 79% was prepared in step (2) of Example 1. Figure 2 The intensity signal marked by the dashed box shows that the second barrier layer with a gradient composition was prepared in step (2) of Example 1.

[0122] Figure 3 This is an atomic force microscope image of the surface of the germanium silicon quantum well material prepared in Example 1 of the present application. Figure 3 It is shown that step (1) and step (2) of Example 1 can make the germanium silicon material follow two-dimensional layered growth, and finally a quantum well material with a flat surface is prepared, and its surface roughness root mean square value (RMS) is 0.94nm.

[0123] Figure 4 It is the secondary ion mass spectrometry (SIMS) spectrum line of the germanium silicon quantum well material prepared in Example 1 of the present application. Figure 4 It shows that the germanium silicon quantum well material prepared in Example 1 has a germanium and silicon component content that changes gradually with depth. As the depth decreases from the surface layer of the material to the potential well layer, the germanium content decreases continuously from 79% to 20%.

[0124] Figure 5 It is a schematic diagram of energy band simulation when voltage is applied to the germanium silicon quantum well material prepared in Example 1 of the present application. Figure 5 It is shown that the germanium silicon quantum well material solves the problem of surface charge accumulation under gate control. When a voltage of -0.5V is applied to the surface of the material, the hole energy level in the potential well layer crosses the Fermi surface, forming a hole filling in the quantum well. At the same time, the hole energy level on the surface of the material is below the Fermi surface, and the hole cannot achieve tunneling from the potential well layer to the surface of the material, so no surface charge accumulation will occur.

[0125] Figure 6 This is the X-ray diffraction surface scan pattern of the germanium silicon quantum well material prepared in Comparative Example 1 of the present application. Figure 6 The intensity peak marked by the middle triangle shows that the step (1) of Comparative Example 1 prepared a germanium silicon buffer layer with a germanium content of 79%. Figure 5 The intensity peak marked by the middle triangle also shows that the first barrier layer and the second barrier layer with a fixed composition of 79% germanium content were prepared in step (2) of Comparative Example 1.

[0126] Figure 7It is a schematic diagram of energy band simulation when voltage is applied to the germanium silicon quantum well material prepared in Comparative Example 1 of the present application. Figure 7 The result shows that the germanium silicon quantum well material in comparative example 1 has the problem of surface charge accumulation under gate control. When a voltage of -0.5V is applied to the surface of the material, the hole energy level on the surface of the material crosses the Fermi surface, and the holes tunnel from the potential well layer to the surface of the material under the electric field, resulting in surface charge accumulation.

[0127] 2. Numerical simulation of the germanium silicon quantum well material of Example 3 of the present application.

[0128] Fig.11 It is a schematic diagram of energy band simulation when voltage is applied to the germanium silicon quantum well material prepared in Example 3 of the present invention. Fig.11 It is shown that the germanium silicon quantum well material solves the problem of surface charge accumulation under gate control. When a voltage of +0.65V is applied to the surface of the material, the electron energy level in the potential well layer crosses the Fermi surface, forming an electron filling in the quantum well. At the same time, the electron energy level on the surface of the material is above the Fermi surface, and the electrons cannot tunnel from the potential well layer to the surface of the material, so no surface charge accumulation will occur.

[0129] According to the test results of the above-mentioned embodiments and comparative examples of the present application, it can be known that the germanium silicon quantum well material provided by the present application has various material layers with component gradients designed by energy band engineering. Unlike the previous germanium silicon quantum wells, when a strong electric field is applied to the material, the carriers no longer tunnel to the surface of the material. This material can effectively solve the problem of surface charge accumulation in germanium silicon gate-controlled quantum devices, improve the decoherence time of germanium silicon quantum bits, improve the electrical transport performance of two-dimensional carrier gas, and improve the energy stability of devices such as gate-controlled quantum dots and field effect transistors.

[0130] The germanium-silicon gate-controlled quantum device prepared using the materials provided in this application has better gate control adjustability, the chemical potential adjustment range of the device functional area is improved, the energy scale range of the device operation is expanded, and the potential application scenarios of related devices can be increased.

[0131] This application uses component gradient and modulation doping to finely plan the band structure of the material. For germanium silicon quantum bits and gate-controlled quantum dot devices, the spatial position and energy of specific electron (hole) states can be precisely controlled, which is conducive to the precise construction of quantum systems and promotes the development of quantum technology.

[0132] The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. It should be noted that, for ordinary technicians in this technical field, several improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A germanium silicon quantum well material, characterized in that: The germanium-silicon quantum well material includes, from bottom to top, a germanium-silicon substrate layer, a germanium-silicon buffer layer, a first barrier layer, a potential well layer, and a second barrier layer; The composition contents of germanium and silicon in at least one of the first barrier layer, the potential well layer and the second barrier layer are in a gradient state; The gradual change state includes gradually increasing, decreasing, and / or fluctuating from bottom to top.

2. The germanium silicon quantum well material according to claim 1, characterized in that: The gradual change state includes: The gradient range of the germanium content in the first barrier layer, the potential well layer and the second barrier layer is 0%-100%, and the corresponding gradient range of the silicon content is 100%-0%; Optionally, the gradual change state includes: continuous gradual change, step-by-step gradual change and periodic gradual change.

3. The germanium silicon quantum well material according to claim 1, characterized in that: The thickness of the first barrier layer and the second barrier layer is 1-150nm; The potential well layer has a thickness of 1-50 nm.

4. The germanium silicon quantum well material according to claim 3, characterized in that: The first barrier layer and the second barrier layer are doped with one or more of boron, aluminum, gallium, indium, phosphorus, arsenic and antimony; Optionally, the doping concentration is 0-1×10 18 cm -3 .

5. The germanium silicon quantum well material according to any one of claims 1 to 4, characterized in that: A spacer layer and a modulation doping layer are provided between the first barrier layer and the potential well layer, and / or between the potential well layer and the second barrier layer; Wherein, the spacer layer is located between the modulation doping layer and the potential well layer.

6. The germanium silicon quantum well material according to claim 5, characterized in that: The thickness of the modulation doping layer is 0-50nm; Optionally, the modulation doping layer is doped with one or more of boron, aluminum, gallium, indium, phosphorus, arsenic and antimony elements; Further optionally, the doping concentration of the modulation doping layer is 1×10 16 -5×10 20 cm -3 .

7. The germanium silicon quantum well material according to claim 5, characterized in that: The thickness of the spacer layer is 0-60nm; Optionally, the germanium element and the silicon element in the spacer layer are in a gradient state, and the gradient range of the germanium element content is 0%-100%; the corresponding gradient range of the silicon element content is 100%-0%.

8. A method for preparing the germanium silicon quantum well material according to any one of claims 1 to 7, characterized in that: include: Pre-treating the silicon germanium substrate layer; epitaxially growing a germanium silicon buffer layer on the first surface of the pre-treated germanium silicon substrate layer; Epitaxially growing a first barrier layer on a surface of the silicon germanium buffer layer away from the silicon germanium substrate layer; Epitaxially growing a potential well layer on a surface of the first barrier layer away from the germanium silicon buffer layer; epitaxially growing a second barrier layer on a surface of the potential well layer away from the first barrier layer; Wherein, the ratio of the growth rates of germanium and silicon is dynamically adjusted during the process of growing at least one of the first barrier layer, the potential well layer and the second barrier layer.

9. The preparation method according to claim 8, characterized in that: Also includes: epitaxially growing a spacer layer and a modulation doping layer; Wherein, the spacer layer is located between the modulation doping layer and the potential well layer.

10. Use of the germanium silicon quantum well material according to any one of claims 1 to 7, and / or the germanium silicon quantum well material prepared by the preparation method according to any one of claims 8 to 9, in precision quantum devices; in, The precision quantum devices include: quantum bits, two-dimensional electron (hole) gas, field effect transistors, and gate-controlled quantum dots.

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